Jute for use as carpet backing thread is in short supply. Attempts have been made to provide plastic tape as a substitute for jute. In the prior art processes for making plastic tape, the processing speed was very slow, permitting stabilizing of the plastic tape in the heating ovens, through which the tape passed to be stretched longitudinally, to a desired thickness.
To make the plastic tape commercially saleable, the process for making the tape had to be speeded up to increase production and lower the cost of manufacture.
Production requirements increased but the ovens remained the same size, resulting in great shrinkage in the plastic tape during processing. Competition between plastic tape manufacturers has caused the manufacturers to look upon the shrinkage as a manufacturing loss.
The stabilizing operation was then performed in a unit separate from the in-line manufacturing process. The tapes were wound upon individual cores. The cores were subject to reheating to perform the stabilizing operation. The result was: first, the tapes wound on the cores shrank beyond allowable commercial limits; and, second, the degree of stability varied with the position of the layer of the tape upon the wound core; and, third, the extra handling increased the cost of manufacture of the tapes.
In the manufacture of plastic tape, a stabilizing operation is necessary to remove the stresses imparted into the tape during the longitudinal stretching operation. Stabilizing requires reheating of the tape. Reheating, heretofore, resulted in unsatisfactory shrinkage.